http://dev.clojure.org/jira This file is an XML representation of an issue en-us 4.4 649 25-07-2011 http://dev.clojure.org/jira/browse/LOGIC-91 core.logic <div class="code panel" style="border-width: 1px;"><div class="codeContent panelContent"> <pre class="code-java">(is (= (run* [q] (nom/fresh [a] (fresh [x] (predc x number? `number?) (== x 1) (== (nom/tie a [a x]) q)))) [(nom/tie 'a_0 '(a_0 1))])) (is (= (run* [q] (nom/fresh [a] (fresh [x] (== x 1) (predc x number? `number?) (== (nom/tie a [a x]) q)))) [(nom/tie 'a_0 '(a_0 1))])) ;; <span class="code-keyword">false</span> b/c of extra :- number? constraint</pre> </div></div> LOGIC-91

nom/tie and spurious reification of predc constraint

Defect Blocker Resolved Completed David Nolen Nada Amin Wed, 2 Jan 2013 04:57:52 -0600 Wed, 2 Jan 2013 08:46:44 -0600 Wed, 2 Jan 2013 08:46:44 -0600 0 0 <p>Implementing -force-ans in Tie</p> <div class="code panel" style="border-width: 1px;"><div class="codeContent panelContent"> <pre class="code-java">clojure.core.logic.IForceAnswerTerm (-force-ans [v x] (force-ans (:body v)))</pre> </div></div> <p>resolves the test above, but not this one:</p> <div class="code panel" style="border-width: 1px;"><div class="codeContent panelContent"> <pre class="code-java">(is (= (run* [q] (nom/fresh [a b c] (fresh [x y] (== x 1) (predc x number? `number?) (== (nom/tie b (nom/tie a [a x])) (nom/tie c q))))) [(nom/tie 'a_0 '(a_0 1))])) ;; still <span class="code-keyword">false</span> b/c of extra :- number? constraint</pre> </div></div> <p>This issue actually impacts any "single shot" constraint that implements `-relevant?` as simply returning `true`. The problem is that the `cgoal` constraint wrapper checks `runnable?`, runs the constraint, and then checks `relevant?` and if that's true adds the constraint even though it may very well may be entailed!</p> <p>There are 6 constraints (1 of them the `defc` macro) which implement `-relevant?` as returning `true`. I think we should have more support (a protocol) for constraints which are essentially "single shot" and don't need to bother with implementing the `IRelevant` protocol.</p> <p>For some background - the CLP(FD) constraints benefit most from the `IRelevant` protocol, where the constraints involve up to 3 terms and a considerable amount of propagation work may be avoided by doing some checking up front.</p> <p>Hi David,</p> <p>I have a fix proposed in pull request <a href="https://github.com/clojure/core.logic/pull/15">https://github.com/clojure/core.logic/pull/15</a></p> <p>The idea there is that to honor single-shot constraints, we only need to honor the (remcg this) that they contain. This is only possible if they have proper ids. That's what I fix.</p> <p>Let me know what you think.</p> <p>fixed, <a href="http://github.com/clojure/core.logic/commit/020f730429d71315f752ea51abad20dca896c8b0">http://github.com/clojure/core.logic/commit/020f730429d71315f752ea51abad20dca896c8b0</a></p> Global Rank